Over 500,000 bone graft procedures are performed annually in the United States, and approximately 2.2 million are performed worldwide with an annual cost of nearly $2.5 billion. These bone graft procedures are routinely performed to not only treat bone fractures and other bone defects, but are also routinely performed to strengthen existing bone that may be deteriorating. Typically, the bone material used for these bone graft procedures is either autograft, which is derived from the patient's own body, or allograft, which is derived from a genetically dissimilar member of the same species. In some cases though, the graft material can even be xenograft, which is taken from another species.
From a biological standpoint, autograft is the preferred type of graft material and the type of material that is most commonly used in many of the orthopedic, maxillofacial, podiatric, and dental surgeries that require bone graft procedures to be performed. Autograft bone materials also exhibit many of the preferred properties for treating a bone defect, including the ability to produce new bone from transplanted living cells and the ability to integrate with the bone tissue at the graft site. Despite these advantages, however, an autograft procedure usually requires that additional surgery be performed on a subject to acquire the graft material, which can lead to complications, such as inflammation or infection. In addition, during these surgeries, only a very limited amount of bone can be collected. As such, allograft and xenograft materials have been developed that provide benefits in terms of the quantity of materials that can be obtained, but those materials still frequently have their own complications, such as disease transmission and graft failure, thus leaving researchers looking for better alternatives.
To that end, many additional types of bone graft compositions have been recently developed, including allograft-based, ceramic-based, and polymer-based compositions. For example, U.S. Pat. No. 7,494,950 describes implantable compositions containing a calcium salt-containing component, optionally demineralized bone, and a plurality of discrete fibers. For another example, U.S. Pat. No. 6,548,080 describes an application for a bone defect site that includes a partially demineralized cortical bone structure. As yet another example, U.S. Pat. No. 6,599,516 describes the inclusion of materials within a moldable ceramic compound capable of hardening, with the specific goal of allowing cellular access to the interior of the implanted material. Nevertheless, despite the many alternative bone graft compositions available today, the currently-available alternative bone graft compositions generally do not possess sufficient strength and are not rapidly or completely incorporated, remodeled, or resorbed by the body of a subject. Thus, they can not be considered as viable alternatives to prior autograft-, allograft-, or xenograft-based bone graft materials. Furthermore, currently-available bone graft compositions do not sufficiently address how certain concentrations or shapes of the bone particles can be incorporated into a bone graft composition in a manner that changes the properties of the composition itself and increases the strength, resorption rate, and rate of incorporation and remodeling of the implanted materials.